oxirs-stream 0.3.1

//! Event serializer/deserializer implementations and supporting encoders.
//!
//! This module provides:
//! - [`EventSerializer`] - format-aware (de)serializer
//! - [`FormatConverter`] - cross-format converter
//! - [`StreamingSerializer`] - batched/streamed serialization
//! - [`EnhancedBinaryFormat`] - chunked binary format with checksums

use anyhow::{anyhow, Result};
use bytes::{Buf, BufMut, Bytes, BytesMut};
use futures::stream::{BoxStream, StreamExt as _};
use std::collections::BTreeMap;
use std::io::Read as _;
use std::sync::Arc;

use crate::serialization_decoder::DeltaCompressor;
use crate::serialization_types::{
    from_avro_value, get_default_avro_schema, to_avro_value, DeltaCompressionType,
    ProtobufStreamEvent, SchemaRegistry, SerializationFormat, SerializerOptions,
};
use crate::{CompressionType, EventMetadata, StreamEvent};
use tokio_stream::Stream;

/// Event serializer with format support
#[derive(Clone)]
pub struct EventSerializer {
    pub(crate) format: SerializationFormat,
    pub(crate) compression: Option<CompressionType>,
    pub(crate) schema_registry: Option<Arc<SchemaRegistry>>,
    pub(crate) options: SerializerOptions,
}

impl EventSerializer {
    /// Create a new event serializer
    pub fn new(format: SerializationFormat) -> Self {
        Self {
            format,
            compression: None,
            schema_registry: None,
            options: SerializerOptions::default(),
        }
    }

    /// Set compression type
    pub fn with_compression(mut self, compression: CompressionType) -> Self {
        self.compression = Some(compression);
        self
    }

    /// Set schema registry
    pub fn with_schema_registry(mut self, registry: Arc<SchemaRegistry>) -> Self {
        self.schema_registry = Some(registry);
        self
    }

    /// Set serializer options
    pub fn with_options(mut self, options: SerializerOptions) -> Self {
        self.options = options;
        self
    }

    /// Serialize a stream event
    pub async fn serialize(&self, event: &StreamEvent) -> Result<Bytes> {
        let mut buffer = BytesMut::new();

        // Add magic bytes if enabled
        if self.options.include_magic_bytes {
            buffer.put(self.format.magic_bytes());
        }

        // Add schema ID if enabled and registry is available
        if self.options.include_schema_id {
            if let Some(registry) = &self.schema_registry {
                let schema_id = registry.get_schema_id_for_event(event).await?;
                buffer.put_u32(schema_id.parse::<u32>().unwrap_or(0));
            }
        }

        // Serialize based on format
        let serialized = match self.format {
            SerializationFormat::Json => self.serialize_json(event)?,
            SerializationFormat::Binary => self.serialize_binary(event)?,
            SerializationFormat::MessagePack => self.serialize_messagepack(event)?,
            SerializationFormat::Cbor => self.serialize_cbor(event)?,
            SerializationFormat::Protobuf => self.serialize_protobuf(event)?,
            SerializationFormat::Avro => self.serialize_avro(event).await?,
        };

        // Apply compression if enabled
        let data = if let Some(compression) = &self.compression {
            self.compress(&serialized, compression)?
        } else {
            serialized
        };

        // Check size limit
        if let Some(max_size) = self.options.max_size {
            if data.len() > max_size {
                return Err(anyhow!(
                    "Serialized data exceeds maximum size: {} > {max_size}",
                    data.len()
                ));
            }
        }

        buffer.put(&data[..]);
        Ok(buffer.freeze())
    }

    /// Deserialize a stream event
    pub async fn deserialize(&self, data: &[u8]) -> Result<StreamEvent> {
        let mut cursor = std::io::Cursor::new(data);
        let mut offset = 0;

        // Skip magic bytes if present
        if self.options.include_magic_bytes && data.len() >= 4 {
            let magic = &data[0..4];
            if magic == self.format.magic_bytes() {
                offset += 4;
                cursor.set_position(4);
            }
        }

        // Skip schema ID if present
        if self.options.include_schema_id
            && self.schema_registry.is_some()
            && data.len() >= offset + 4
        {
            offset += 4;
            cursor.set_position(offset as u64);
        }

        // Get remaining data
        let event_data = &data[offset..];

        // Decompress if needed
        let decompressed = if let Some(compression) = &self.compression {
            self.decompress(event_data, compression)?
        } else {
            event_data.to_vec()
        };

        // Deserialize based on format
        match self.format {
            SerializationFormat::Json => self.deserialize_json(&decompressed),
            SerializationFormat::Binary => self.deserialize_binary(&decompressed),
            SerializationFormat::MessagePack => self.deserialize_messagepack(&decompressed),
            SerializationFormat::Cbor => self.deserialize_cbor(&decompressed),
            SerializationFormat::Protobuf => self.deserialize_protobuf(&decompressed),
            SerializationFormat::Avro => self.deserialize_avro(&decompressed).await,
        }
    }

    /// Serialize to JSON
    fn serialize_json(&self, event: &StreamEvent) -> Result<Vec<u8>> {
        if self.options.pretty_json {
            serde_json::to_vec_pretty(event).map_err(|e| anyhow!("JSON serialization failed: {e}"))
        } else {
            serde_json::to_vec(event).map_err(|e| anyhow!("JSON serialization failed: {e}"))
        }
    }

    /// Deserialize from JSON
    fn deserialize_json(&self, data: &[u8]) -> Result<StreamEvent> {
        serde_json::from_slice(data).map_err(|e| anyhow!("JSON deserialization failed: {e}"))
    }

    /// Serialize to binary format
    fn serialize_binary(&self, event: &StreamEvent) -> Result<Vec<u8>> {
        // Custom binary format implementation
        let mut buffer = Vec::new();

        // Write version
        buffer.push(1); // Version 1

        // Write event type
        let event_type = match event {
            StreamEvent::TripleAdded { .. } => 1,
            StreamEvent::TripleRemoved { .. } => 2,
            StreamEvent::QuadAdded { .. } => 3,
            StreamEvent::QuadRemoved { .. } => 4,
            StreamEvent::GraphCreated { .. } => 5,
            StreamEvent::GraphCleared { .. } => 6,
            StreamEvent::GraphDeleted { .. } => 7,
            StreamEvent::GraphMetadataUpdated { .. } => 17,
            StreamEvent::GraphPermissionsChanged { .. } => 18,
            StreamEvent::GraphStatisticsUpdated { .. } => 19,
            StreamEvent::GraphRenamed { .. } => 20,
            StreamEvent::GraphMerged { .. } => 21,
            StreamEvent::GraphSplit { .. } => 22,
            StreamEvent::SparqlUpdate { .. } => 8,
            StreamEvent::TransactionBegin { .. } => 9,
            StreamEvent::TransactionCommit { .. } => 10,
            StreamEvent::TransactionAbort { .. } => 11,
            StreamEvent::SchemaChanged { .. } => 12,
            StreamEvent::SchemaDefinitionAdded { .. } => 23,
            StreamEvent::SchemaDefinitionRemoved { .. } => 24,
            StreamEvent::SchemaDefinitionModified { .. } => 25,
            StreamEvent::OntologyImported { .. } => 26,
            StreamEvent::OntologyRemoved { .. } => 27,
            StreamEvent::ConstraintAdded { .. } => 28,
            StreamEvent::ConstraintRemoved { .. } => 29,
            StreamEvent::ConstraintViolated { .. } => 30,
            StreamEvent::IndexCreated { .. } => 31,
            StreamEvent::IndexDropped { .. } => 32,
            StreamEvent::IndexRebuilt { .. } => 33,
            StreamEvent::ShapeAdded { .. } => 34,
            StreamEvent::ShapeRemoved { .. } => 35,
            StreamEvent::ShapeModified { .. } => 36,
            StreamEvent::ShapeValidationStarted { .. } => 37,
            StreamEvent::ShapeValidationCompleted { .. } => 38,
            StreamEvent::ShapeViolationDetected { .. } => 39,
            StreamEvent::QueryResultAdded { .. } => 14,
            StreamEvent::QueryResultRemoved { .. } => 15,
            StreamEvent::QueryCompleted { .. } => 16,
            StreamEvent::SchemaUpdated { .. } => 40,
            StreamEvent::ShapeUpdated { .. } => 41,
            StreamEvent::Heartbeat { .. } => 13,
            StreamEvent::ErrorOccurred { .. } => 42,
        };
        buffer.push(event_type);

        // Serialize fields based on event type
        match event {
            StreamEvent::TripleAdded {
                subject,
                predicate,
                object,
                graph,
                metadata,
            } => {
                self.write_string(&mut buffer, subject);
                self.write_string(&mut buffer, predicate);
                self.write_string(&mut buffer, object);
                self.write_optional_string(&mut buffer, graph.as_deref());
                self.write_metadata(&mut buffer, metadata)?;
            }
            // ... implement other event types similarly
            _ => {
                return Err(anyhow!(
                    "Binary serialization not implemented for this event type"
                ))
            }
        }

        Ok(buffer)
    }

    /// Helper to write string to binary buffer
    fn write_string(&self, buffer: &mut Vec<u8>, s: &str) {
        let bytes = s.as_bytes();
        buffer.extend_from_slice(&(bytes.len() as u32).to_le_bytes());
        buffer.extend_from_slice(bytes);
    }

    /// Helper to write optional string
    fn write_optional_string(&self, buffer: &mut Vec<u8>, s: Option<&str>) {
        match s {
            Some(s) => {
                buffer.push(1); // Present
                self.write_string(buffer, s);
            }
            None => {
                buffer.push(0); // Not present
            }
        }
    }

    /// Helper to write metadata
    fn write_metadata(&self, buffer: &mut Vec<u8>, metadata: &EventMetadata) -> Result<()> {
        // Serialize metadata as JSON for simplicity
        let metadata_json = serde_json::to_vec(metadata)?;
        buffer.extend_from_slice(&(metadata_json.len() as u32).to_le_bytes());
        buffer.extend_from_slice(&metadata_json);
        Ok(())
    }

    /// Deserialize from binary format
    fn deserialize_binary(&self, data: &[u8]) -> Result<StreamEvent> {
        if data.len() < 2 {
            return Err(anyhow!("Binary data too short"));
        }

        let version = data[0];
        if version != 1 {
            return Err(anyhow!("Unsupported binary format version: {version}"));
        }

        let event_type = data[1];
        let mut cursor = std::io::Cursor::new(&data[2..]);

        match event_type {
            1 => {
                // TripleAdded
                let subject = self.read_string(&mut cursor)?;
                let predicate = self.read_string(&mut cursor)?;
                let object = self.read_string(&mut cursor)?;
                let graph = self.read_optional_string(&mut cursor)?;
                let metadata = self.read_metadata(&mut cursor)?;

                Ok(StreamEvent::TripleAdded {
                    subject,
                    predicate,
                    object,
                    graph,
                    metadata,
                })
            }
            // ... implement other event types
            _ => Err(anyhow!("Unknown event type: {event_type}")),
        }
    }

    /// Helper to read string from cursor
    fn read_string(&self, cursor: &mut std::io::Cursor<&[u8]>) -> Result<String> {
        use std::io::Read;

        let mut len_bytes = [0u8; 4];
        cursor.read_exact(&mut len_bytes)?;
        let len = u32::from_le_bytes(len_bytes) as usize;

        let mut bytes = vec![0u8; len];
        cursor.read_exact(&mut bytes)?;

        String::from_utf8(bytes).map_err(|e| anyhow!("Invalid UTF-8: {e}"))
    }

    /// Helper to read optional string
    fn read_optional_string(&self, cursor: &mut std::io::Cursor<&[u8]>) -> Result<Option<String>> {
        use std::io::Read;

        let mut present = [0u8; 1];
        cursor.read_exact(&mut present)?;

        if present[0] == 1 {
            Ok(Some(self.read_string(cursor)?))
        } else {
            Ok(None)
        }
    }

    /// Helper to read metadata
    fn read_metadata(&self, cursor: &mut std::io::Cursor<&[u8]>) -> Result<EventMetadata> {
        use std::io::Read;

        let mut len_bytes = [0u8; 4];
        cursor.read_exact(&mut len_bytes)?;
        let len = u32::from_le_bytes(len_bytes) as usize;

        let mut json_bytes = vec![0u8; len];
        cursor.read_exact(&mut json_bytes)?;

        serde_json::from_slice(&json_bytes).map_err(|e| anyhow!("Failed to parse metadata: {e}"))
    }

    /// Serialize to MessagePack
    fn serialize_messagepack(&self, event: &StreamEvent) -> Result<Vec<u8>> {
        rmp_serde::to_vec(event).map_err(|e| anyhow!("MessagePack serialization failed: {e}"))
    }

    /// Deserialize from MessagePack
    fn deserialize_messagepack(&self, data: &[u8]) -> Result<StreamEvent> {
        rmp_serde::from_slice(data).map_err(|e| anyhow!("MessagePack deserialization failed: {e}"))
    }

    /// Serialize to CBOR
    fn serialize_cbor(&self, event: &StreamEvent) -> Result<Vec<u8>> {
        let mut buf = Vec::new();
        ciborium::ser::into_writer(event, &mut buf)
            .map_err(|e| anyhow!("CBOR serialization failed: {e}"))?;
        Ok(buf)
    }

    /// Deserialize from CBOR
    fn deserialize_cbor(&self, data: &[u8]) -> Result<StreamEvent> {
        ciborium::de::from_reader(data).map_err(|e| anyhow!("CBOR deserialization failed: {e}"))
    }

    /// Serialize to Protocol Buffers
    fn serialize_protobuf(&self, event: &StreamEvent) -> Result<Vec<u8>> {
        // Use prost for Protocol Buffers serialization
        // For now, we'll use a JSON-based approach until proper proto definitions are created
        let json_data = serde_json::to_value(event)?;
        let proto_event = ProtobufStreamEvent::from_json(&json_data)?;

        let mut buf = Vec::new();
        prost::Message::encode(&proto_event, &mut buf)?;
        Ok(buf)
    }

    /// Deserialize from Protocol Buffers
    fn deserialize_protobuf(&self, data: &[u8]) -> Result<StreamEvent> {
        let proto_event = ProtobufStreamEvent::decode(data)?;
        let json_value = proto_event.to_json()?;
        let event: StreamEvent = serde_json::from_value(json_value)?;
        Ok(event)
    }

    /// Serialize to Apache Avro
    async fn serialize_avro(&self, event: &StreamEvent) -> Result<Vec<u8>> {
        // Get schema from registry if available
        let schema = if let Some(registry) = &self.schema_registry {
            registry.get_avro_schema_for_event(event).await?
        } else {
            // Use default schema
            get_default_avro_schema()
        };

        // Convert event to Avro value
        let avro_value = to_avro_value(event, &schema)?;

        // Serialize with schema
        let mut writer = Vec::new();
        let mut encoder = apache_avro::Writer::new(&schema, &mut writer);
        encoder.append(avro_value)?;
        encoder.flush()?;

        // apache-avro 0.21: extract the writer before encoder is dropped
        let result = encoder.into_inner()?.to_vec();
        Ok(result)
    }

    /// Deserialize from Apache Avro
    async fn deserialize_avro(&self, data: &[u8]) -> Result<StreamEvent> {
        // Extract schema from data header
        let reader = apache_avro::Reader::new(data)?;
        let schema = reader.writer_schema().clone();

        // Read the first (and only) record
        if let Some(record) = reader.into_iter().next() {
            let avro_value = record?;
            let event = from_avro_value(&avro_value, &schema)?;
            Ok(event)
        } else {
            Err(anyhow!("No Avro record found in data"))
        }
    }

    /// Compress data
    fn compress(&self, data: &[u8], compression: &CompressionType) -> Result<Vec<u8>> {
        match compression {
            CompressionType::None => Ok(data.to_vec()),
            CompressionType::Gzip => oxiarc_deflate::gzip_compress(data, 6)
                .map_err(|e| anyhow!("Gzip compression failed: {e}")),
            CompressionType::Zstd => oxiarc_zstd::encode_all(data, 3)
                .map_err(|e| anyhow!("Zstd compression failed: {e}")),
            CompressionType::Lz4 => {
                oxiarc_lz4::compress(data).map_err(|e| anyhow!("LZ4 compression failed: {e}"))
            }
            CompressionType::Snappy => Ok(oxiarc_snappy::compress(data)),
        }
    }

    /// Decompress data
    fn decompress(&self, data: &[u8], compression: &CompressionType) -> Result<Vec<u8>> {
        match compression {
            CompressionType::None => Ok(data.to_vec()),
            CompressionType::Gzip => oxiarc_deflate::gzip_decompress(data)
                .map_err(|e| anyhow!("Gzip decompression failed: {e}")),
            CompressionType::Zstd => {
                oxiarc_zstd::decode_all(data).map_err(|e| anyhow!("Zstd decompression failed: {e}"))
            }
            CompressionType::Lz4 => oxiarc_lz4::decompress(data, 100 * 1024 * 1024)
                .map_err(|e| anyhow!("LZ4 decompression failed: {e}")),
            CompressionType::Snappy => oxiarc_snappy::decompress(data)
                .map_err(|e| anyhow!("Snappy decompression failed: {e}")),
        }
    }
}

/// Format converter for converting between serialization formats
pub struct FormatConverter {
    source_format: SerializationFormat,
    target_format: SerializationFormat,
    #[allow(dead_code)]
    schema_registry: Option<Arc<SchemaRegistry>>,
}

impl FormatConverter {
    /// Create a new format converter
    pub fn new(source: SerializationFormat, target: SerializationFormat) -> Self {
        Self {
            source_format: source,
            target_format: target,
            schema_registry: None,
        }
    }

    /// Convert data between formats
    pub async fn convert(&self, data: &[u8]) -> Result<Bytes> {
        // Deserialize from source format
        let source_serializer = EventSerializer::new(self.source_format);
        let event = source_serializer.deserialize(data).await?;

        // Serialize to target format
        let target_serializer = EventSerializer::new(self.target_format);
        target_serializer.serialize(&event).await
    }
}

/// Streaming serializer for batch processing
pub struct StreamingSerializer {
    serializer: EventSerializer,
    delta_compressor: Option<DeltaCompressor>,
    batch_size: usize,
    current_batch: Vec<StreamEvent>,
}

impl StreamingSerializer {
    /// Create a new streaming serializer
    pub fn new(serializer: EventSerializer, batch_size: usize) -> Self {
        Self {
            serializer,
            delta_compressor: None,
            batch_size,
            current_batch: Vec::new(),
        }
    }

    /// Enable delta compression
    pub fn with_delta_compression(
        mut self,
        compression_type: DeltaCompressionType,
        max_states: usize,
    ) -> Self {
        self.delta_compressor = Some(DeltaCompressor::new(compression_type, max_states));
        self
    }

    /// Add event to batch
    pub async fn add_event(&mut self, event: StreamEvent) -> Result<Option<Bytes>> {
        self.current_batch.push(event);

        if self.current_batch.len() >= self.batch_size {
            self.flush_batch().await
        } else {
            Ok(None)
        }
    }

    /// Flush current batch
    pub async fn flush_batch(&mut self) -> Result<Option<Bytes>> {
        if self.current_batch.is_empty() {
            return Ok(None);
        }

        let batch = std::mem::take(&mut self.current_batch);
        let serialized = self.serialize_batch(&batch).await?;
        Ok(Some(serialized))
    }

    /// Serialize a batch of events
    async fn serialize_batch(&self, batch: &[StreamEvent]) -> Result<Bytes> {
        let mut buffer = BytesMut::new();

        // Write batch header
        buffer.put_u32(batch.len() as u32);
        buffer.put_u64(chrono::Utc::now().timestamp_millis() as u64);

        // Serialize each event
        for event in batch {
            let event_data = self.serializer.serialize(event).await?;
            buffer.put_u32(event_data.len() as u32);
            buffer.put(event_data);
        }

        Ok(buffer.freeze())
    }

    /// Deserialize a batch of events
    pub async fn deserialize_batch(&self, data: &[u8]) -> Result<Vec<StreamEvent>> {
        let mut cursor = std::io::Cursor::new(data);
        let mut events = Vec::new();

        // Read batch header
        let batch_size = cursor.get_u32();
        let _timestamp = cursor.get_u64();

        // Read each event
        for _ in 0..batch_size {
            let event_size = cursor.get_u32() as usize;
            let event_data =
                &data[cursor.position() as usize..(cursor.position() as usize + event_size)];
            cursor.advance(event_size);

            let event = self.serializer.deserialize(event_data).await?;
            events.push(event);
        }

        Ok(events)
    }

    /// Create a stream of serialized batches
    pub fn create_batch_stream(
        &self,
        events: impl Stream<Item = StreamEvent> + Send + 'static,
    ) -> BoxStream<'static, Result<Bytes>> {
        let serializer = self.serializer.clone();
        let batch_size = self.batch_size;

        Box::pin(events.chunks(batch_size).then(move |chunk| {
            let serializer = serializer.clone();
            async move {
                let streaming_serializer = StreamingSerializer::new(serializer, batch_size);
                streaming_serializer.serialize_batch(&chunk).await
            }
        }))
    }
}

/// Enhanced binary format with streaming support
pub struct EnhancedBinaryFormat {
    version: u8,
    enable_compression: bool,
    enable_checksums: bool,
    chunk_size: usize,
}

impl EnhancedBinaryFormat {
    /// Create a new enhanced binary format
    pub fn new() -> Self {
        Self {
            version: 2, // Enhanced version
            enable_compression: true,
            enable_checksums: true,
            chunk_size: 8192, // 8KB chunks
        }
    }

    /// Configure compression
    pub fn with_compression(mut self, enable: bool) -> Self {
        self.enable_compression = enable;
        self
    }

    /// Configure checksums
    pub fn with_checksums(mut self, enable: bool) -> Self {
        self.enable_checksums = enable;
        self
    }

    /// Set chunk size for streaming
    pub fn with_chunk_size(mut self, size: usize) -> Self {
        self.chunk_size = size;
        self
    }

    /// Serialize event in enhanced binary format
    pub async fn serialize(&self, event: &StreamEvent) -> Result<Bytes> {
        let mut buffer = BytesMut::new();

        // Header
        buffer.put(&b"BIN2"[..]); // Magic bytes for v2
        buffer.put_u8(self.version);
        buffer.put_u8(self.get_flags());

        // Serialize event data
        let event_json = serde_json::to_vec(event)?;

        // Apply compression if enabled
        let data = if self.enable_compression {
            oxiarc_lz4::compress(&event_json)
                .map_err(|e| anyhow!("LZ4 compression failed: {}", e))?
        } else {
            event_json
        };

        // Add checksum if enabled
        if self.enable_checksums {
            let checksum = crc32fast::hash(&data);
            buffer.put_u32(checksum);
        }

        // Add data length and data
        buffer.put_u32(data.len() as u32);
        buffer.put(&data[..]);

        Ok(buffer.freeze())
    }

    /// Deserialize event from enhanced binary format
    pub async fn deserialize(&self, data: &[u8]) -> Result<StreamEvent> {
        let mut cursor = std::io::Cursor::new(data);

        // Check magic bytes
        let mut magic = [0u8; 4];
        cursor.read_exact(&mut magic)?;
        if &magic != b"BIN2" {
            return Err(anyhow!("Invalid magic bytes for enhanced binary format"));
        }

        // Read version and flags
        let version = cursor.get_u8();
        if version != self.version {
            return Err(anyhow!(
                "Unsupported enhanced binary format version: {}",
                version
            ));
        }

        let flags = cursor.get_u8();
        let has_compression = (flags & 0x01) != 0;
        let has_checksum = (flags & 0x02) != 0;

        // Read checksum if present
        let expected_checksum = if has_checksum {
            Some(cursor.get_u32())
        } else {
            None
        };

        // Read data
        let data_len = cursor.get_u32() as usize;
        let mut event_data = vec![0u8; data_len];
        cursor.read_exact(&mut event_data)?;

        // Verify checksum
        if let Some(expected) = expected_checksum {
            let actual = crc32fast::hash(&event_data);
            if actual != expected {
                return Err(anyhow!(
                    "Checksum mismatch: expected {}, got {}",
                    expected,
                    actual
                ));
            }
        }

        // Decompress if needed
        let decompressed = if has_compression {
            oxiarc_lz4::decompress(&event_data, 100 * 1024 * 1024)
                .map_err(|e| anyhow!("LZ4 decompression failed: {}", e))?
        } else {
            event_data
        };

        // Deserialize event
        let event = serde_json::from_slice(&decompressed)?;
        Ok(event)
    }

    /// Create streaming chunks for large events
    pub async fn serialize_streaming(&self, event: &StreamEvent) -> Result<Vec<Bytes>> {
        let serialized = self.serialize(event).await?;
        let mut chunks = Vec::new();

        if serialized.len() <= self.chunk_size {
            chunks.push(serialized);
        } else {
            // Split into chunks
            let chunk_count = (serialized.len() + self.chunk_size - 1) / self.chunk_size;

            for i in 0..chunk_count {
                let start = i * self.chunk_size;
                let end = std::cmp::min(start + self.chunk_size, serialized.len());

                let mut chunk_buffer = BytesMut::new();
                chunk_buffer.put(&b"CHNK"[..]); // Chunk magic
                chunk_buffer.put_u32(i as u32); // Chunk index
                chunk_buffer.put_u32(chunk_count as u32); // Total chunks
                chunk_buffer.put_u32((end - start) as u32); // Chunk size
                chunk_buffer.put(&serialized[start..end]);

                chunks.push(chunk_buffer.freeze());
            }
        }

        Ok(chunks)
    }

    /// Reassemble streaming chunks
    pub async fn deserialize_streaming(&self, chunks: Vec<Bytes>) -> Result<StreamEvent> {
        if chunks.len() == 1 && !chunks[0].starts_with(b"CHNK") {
            // Single chunk, deserialize directly
            return self.deserialize(&chunks[0]).await;
        }

        // Reassemble chunks
        let mut chunk_data: BTreeMap<u32, Vec<u8>> = BTreeMap::new();
        let mut total_chunks = 0;

        for chunk in chunks {
            if !chunk.starts_with(b"CHNK") {
                return Err(anyhow!("Invalid chunk format"));
            }

            let mut cursor = std::io::Cursor::new(&chunk[4..]);
            let chunk_index = cursor.get_u32();
            let chunk_count = cursor.get_u32();
            let chunk_size = cursor.get_u32() as usize;

            total_chunks = chunk_count;

            let data = chunk[16..16 + chunk_size].to_vec();
            chunk_data.insert(chunk_index, data);
        }

        if chunk_data.len() != total_chunks as usize {
            return Err(anyhow!(
                "Missing chunks: got {}, expected {}",
                chunk_data.len(),
                total_chunks
            ));
        }

        // Reassemble data
        let mut reassembled = Vec::new();
        for (_index, data) in chunk_data {
            reassembled.extend(data);
        }

        // Deserialize reassembled data
        self.deserialize(&reassembled).await
    }

    /// Get format flags
    fn get_flags(&self) -> u8 {
        let mut flags = 0u8;
        if self.enable_compression {
            flags |= 0x01;
        }
        if self.enable_checksums {
            flags |= 0x02;
        }
        flags
    }
}

impl Default for EnhancedBinaryFormat {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(test)]
mod compression_tests {
    use super::*;

    fn serializer() -> EventSerializer {
        EventSerializer::new(SerializationFormat::Json)
    }

    /// Raw-Snappy round-trip via oxiarc_snappy::compress / decompress.
    #[test]
    fn test_raw_snappy_round_trip() {
        let ser = serializer();
        let data = b"serialization encoder raw snappy payload ".repeat(48);
        let compressed = ser
            .compress(&data, &CompressionType::Snappy)
            .expect("snappy compress");
        let restored = ser
            .decompress(&compressed, &CompressionType::Snappy)
            .expect("snappy decompress");
        assert_eq!(restored, data, "raw snappy round-trip mismatch");
    }

    /// Raw-Snappy must round-trip an incompressible/random buffer.
    #[test]
    fn test_raw_snappy_round_trip_random() {
        use scirs2_core::random::Random;
        use scirs2_core::RngExt;
        let mut rng = Random::default();
        let data: Vec<u8> = (0..2048).map(|_| rng.random()).collect();

        let ser = serializer();
        let compressed = ser
            .compress(&data, &CompressionType::Snappy)
            .expect("snappy compress random");
        let restored = ser
            .decompress(&compressed, &CompressionType::Snappy)
            .expect("snappy decompress random");
        assert_eq!(restored, data, "raw snappy random round-trip mismatch");
    }

    /// Gzip round-trip via oxiarc_deflate::gzip_compress / gzip_decompress.
    #[test]
    fn test_gzip_round_trip() {
        let ser = serializer();
        let data = b"serialization encoder gzip payload ".repeat(40);
        let compressed = ser
            .compress(&data, &CompressionType::Gzip)
            .expect("gzip compress");
        let restored = ser
            .decompress(&compressed, &CompressionType::Gzip)
            .expect("gzip decompress");
        assert_eq!(restored, data, "gzip round-trip mismatch");
    }
}